RepRapFirmware - M569 to run three Z stepper drivers?

I had an interesting thought on bed leveling; it hinges on the use (abuse) of M569, however, using DC42's fork of the RepRapFirmware.

I want to have 3 Z drivers, each with their own Z motor; can I use M569 (or another gcode) to have all three move simultaneously? That would be the default during printing.

To level, I would use M569 to do fine leveling of one Z at a time - after moving the nozzle and a capacitance sensor into place, of course.


Reading the gcode entry, though, only one driver can be assigned to each axis - is that still a limitation? Any way around it?

Thanks!
Paul

Using 3 independently-driven Z motors to do bed levelling is on my todo list for RepRapFirmware. I can't say when it will be implemented because my priority at present is to finish the firmware for the next-generation Duet.

I don't advise using capacitive sensors because they are affected too much by temperature and humidity.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
Using 3 independently-driven Z motors to do bed levelling is on my todo list for RepRapFirmware. I can't say when it will be implemented because my priority at present is to finish the firmware for the next-generation Duet.

That's interesting. How would one wire 3 Z motors to the Duet for independent control?

You would use the DueX4 expansion board to provide an extra motor driver, as the Duet 0.8.5 has only 5.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Duet X4 gives 4 extra steppers doesn't it? If my new TBA printer had 3off Z steppers, and 1 off for each x and y that makes 5. Then I'll need 3 extruders for the Diamond hot end making a total of 8 steppers. A Duet 0.8.5 plus a Due X4 will give me total of 9 possible therefore it's doable yes?

My RRP Mendel 3 uses 2 off Z steppers but they are wired to the same channel (at least I think they are). Are there likely to be any issues keeping 3 steppers in sync if they are controlled from separate channels?

The main issue with keeping multiple Z steppers in sync is that when you power them off and on again, each one will jump to a nearby full step position, and they may not all jump in the same direction. Running a bed levelling procedure that adjusts them independently before printing would make that immaterial. Keeping them in sync after that should not be a problem unless you have a mechanical issue that causes the motors to miss steps.

The Duet 0.8.5 + DueX4 does indeed support up to 9 stepper motors controlled independently.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].